Project Summary It is becoming increasingly evident that plasticity within supraspinal networks, induced by therapeutic interventions, is necessary for optimal recovery of function after spinal cord injury. We have developed a novel combination therapy of motorized bike, 5-HT replacement therapy and treadmill training that can restore open-field weight-supported stepping (BBB score >9) in animals with complete spinal transection. Our preliminary data suggest that both supraspinal neuronal and glial plasticity modulated by therapy and that they influence each other. The central hypothesis of this proposal is that therapy combined with strategies to either promote beneficial neural/glial plasticity and/or attenuate deleterious plasticity (e.g., astrogliosis and inflammation) will enhance supraspinal remodeling and improve functional outcome. This Aim will be addressed with two Specific Aims. Aim 1: Investigate the impact of therapy on functional recovery and supraspinal plasticity after SCI as measured by changes in neurons and glial cells and their relationship to functional recovery. Aim 2: Determine if combining NCTherapy with: (A) strategies to enhance supraspinal plasticity (e.g. via brain-machine interface (BMI) training) and/or (B) inhibiting aspects of reactive gliosis (e.g. modulate TNF activity) is more effective than NCTherapy alone in improving functional recovery after SCI. The results of this work will aid in the development of therapies for recovery of volitional control of movement. Moreover, results could be used for translational research to develop assistive devices to maintain balance (e.g. cortical control of an exoskeleton or functional electrical stimulation). Glial plasticity is defined as a change in the number and or ?activation? of astrocytes and microglia in response to SCI or therapy after SCI. Neuronal plasticity includes changes in the organization of sensorimotor cortex and in neuronal firing patterns that carry information about sensory and motor events. The combined Bethea and Moxon labs have extensive experience measuring and manipulating glial and neuronal plasticity after spinal cord injury. By combining expertise, we can address, for the first time, how these two systems, neuronal and glial, interact to promote functional recovery. We will compare results from a series of 9 Experiments in animals with a complete spinal transection to those with a severe spinal contusion. These Experiments will assess electrophysiology changes (Experiments 1-4), the effect of lesioning the reorganized cortex (Experiment 5) and trace the source of this reorganization (Experiment 6). In Experiment 7, the impact of therapy on differences in spared fibers that cross the lesion will be measured. Finally, difference in the proteins/ genes associated with neuroplasticity and inflammation in the brains of animals will be compared between transected and contused animals (Experiments 8 and 9).